Quinacridone pigment compositions



Dec. 8, 1964 F. F. EHRICH QUINACRIDONE PIGMENT COMPOSITIONS 8 Sheets-Sheet 1 Filed April 25, 1960 llSNBlNI FELIX FREDERICK EHRICH M wozm zE R m .m m wn s m ;l msm w v E E NZ v n o Secgwl. .v 89a mo om o moi w ow mantas. .2291@ .rlll o 22:95-26 32h50, ov o moow mante: Q m n 0 22; l $9 o $0@ zoEjom 9.6m

Dec. 8, 1964 F. F. EHRICH 3,160,510

QUINACRIDONE PIGMENT COMPOSITIONS I Filed April 25. 1960 8 Sheets-Sheet 2 60 /,e phase QA P YS XTURE H ICAL MI 40 phase 4, II-dchloro QA SOLID SOLUTION- 60 o/o QA, 40/Q 4,||-dchl0ro QA ANGLE 2e 3o 25% 2o"o I5o Ioo 5 o INTERPLANAR 3.oeA 356A 4.44A 5.90A 8.84A FASSA SPAcING l I I I I I vIl I II I I EXAMPLE 3A- PHYSICAL MIXTURE I I I I I I I EXAMPLE sA-SoLID SOLUTION |l I I I I I I EXAMPLE SB- PHYSICAL MIXTURE INVENTOR FELIX FREDERICK EHRICH EXAMPLE 3B ISOLID SOLUTION I I I 1 IIIGLE 2e 50 25. I5". Io. 5 IIITER- 5.08A 356A 4.44A 5.90A 8.84A |'I.66A

PLANAR SPACING ATTORNEY Dec. 8, 1964 F. F. EHRlcH 3,160,510

QUINACRIDONE PIGMENT COMPOSITIONS Filed April 25, 1960 ANGLE 29 INTERPLAMAR SPACIIIG 8 Sheets-Sheet. 3

EXAMPLE 4E PHYSICAL MIXTURE EXAMPLE 4E --SOLID SOLUTION EXAMPLE 4J PHYSICAL M IXTURE I EXAMPLHIJ soun lsoLuTlon I l 50, 25, 20a 15, |o, 5a 108A 156A 4.4M 5.9m aan 11.66A

F I G. 4

INVENTOR FELIX FREDERICK EHRICH ATTORNEY Dec. 8,r 1964 Filed Apr-11 25,

F. F. EHRlCH QUINACRIDONE PIGMENT COMPOSITIONS EXAMPLE 5BPHYSIC LMIXTURE EXAMPLE 5B SOLID SOLUTION I III EXAMPLE 5C PHYSICAL MIXTURE ANGLE 26 30 o INTERPLANAR 3.08A

SPACING .EXAMPLE sc-soLlD soLuTloN, 20o |5 o |o o 4.44A 5.90A a.e4A

INVENTOR FELIX FREDERICK EHRICH ATTORNEY Dec 3, 1964 F. F. EHRlcH 3,160,510

QUINACRIDONE PIGMENT COMPOSITIONS Filed April 25. 1.960 8 sheets-sheet 5 l I I I l I I I I EXAMPLE 6A PHYSICAL MIXTURE G 6 EXAMPLE sDPHYs|cA-M|xTuRE |II|| III Il Il EXAMPLE 6F PHYSICAL MIXTURE I I EXAMPLES 6 (A-H) AS SOLII) SOLUTIONS ANGLE ze 30' 25% 2o"o |5 |oo 5 o INTERPLANAR 3.08K A 3.56A 4.44A 5.9oA 8.84A 17.66A

sPAclNG EXAMPLE lo soL-lo SOLUTION INVENTOR I A fEux' FREoERlcK EHRlcH I I I EXAMPLE soLm soLuTloN ANGLE 28 30 25 20 |50 o |00 5o o .5 INTERPLAN-a 5.563 4.44K 5.9oA 8.84 mssAgZm'W AR sPAclNG ATTORNEY l Dec. 8, 1964 F. F. EHRlcH 3,160,510 v QU IIIIIIIIIIIIIIII T CO OOOOOOOO NS Filed April 25, 1960 8 Sheets-Sheet 6 4 I d chloroquinocridone `Fla@ Dec. 8, 1964 F. F. EHRICH 3,160,510

QUINACRIDONE PIGMENT COMPOSITIONS 8 Sheets-Sheet 7 Filed April 25.1960

Quinocridone Qunacridone v INV EN TOR FELIX FREDERICK EHRICH ATTORNEY Dec..8, 1964 F. F. EHRlcH 3,160,510

, QUINACRIDONE PIGMENT COMPOSITIQNS Filed April 25. 1960 8 Sheets-Sheet 8 lll,

INVENTOR ELIX FREDERICK EHRICH BY Wg@ ATTORNEY 219' dichloroquinacfidone United States Patent O 3,160,510 QUINACRIDGNE PIGMENT CGMPOSITIQNS Felix Frederick Ehrich, Westfield, NJ., assigner' to E. I. du Pont de Nemours and Company, Wilmington, Del., a corporation of Delaware Filed A111225, 1960, Ser. No. 24,483 18 Claims. (Cl. 106-288) This invention relates to new quinacridone compositions and to methods of preparing thesene'w compositions.

The quinacridone series of compounds has been described in various literature references and in U.S. patents. The present invention resides in the discovery that quinacridones and related compounds will, under certain conditions, mix with each other to form solid solutions which are quite different from both physical mixtures of such compounds and from the compounds themselves.

The term solid solution which has been used to characterize the new products of this invention is a well recognized term in the study of the properties of solid substances. It is defined in Websters Dictionary as a solid, homogeneous mixture of two or more constituents which may vary in composition between certain limits and remain homogeneous. This phenomenon is discussed at length in many physical chemistry texts such as in the Textbook of Physical Chemistry*Samuel Glasstone- 2d edition, 1946, New York, p. 349 if. In a solid solution, the molecules of the components enter into the saine crystal lattice, usually, but' not always, that of one of the components. The X-ray pattern of the resulting crystalline solid is characteristic of that solid and can be 'clearly differentiated from the pattern of a physical mixture of the same components inthe same proportion. In such physical mixtures, the X-ray lines of each of the components can be distinguished, and the disappearance of many of these lines is one of the criteria of the formation of a solid solution.

In this invention, there are two important properties of the new products formed which render them particularly useful as pigments. In contrast to simple physical` mixtures wherein the color is usually a direct function of the additive effects of the two or more components, these solid solutions give unexpected and unpredictable tinctorial values. It is impossible to generalize about the direction or degree of color shift, and this is additional evidence of the unpredictability of the phenomenon.

The second valuable property isa remarkable enhancement of lightfastness which frequently accompanies the formation of solid solution. In physical mixtures of two pigments, on exposure to light, the components show their individual behaviors frequently resulting in marked changes of hue as one fades more than the other. In contrast, the new solid solutions behave as single substances with respect to any change in hue and characteristically show superior lightfastness even in this field vof quinacridones in which lightfastness is generally good.

Compounds which may be components of the solid solutions of this invention include the linear quinacridones having the following structural formula:

where X is F, Cl, Br, lower alkyl, lower alkoxy, or combinations of these groups, and m and n are integers of from 0-2, both limits being included. The lower alkyl substituents in the above formula include methyl, ethyl, propyl, isopropyl, butyl, isobutyl, and tert. butyl. The lower alkoxysubstituents may be vmethoxy, ethoxy, propoxy, isopropoxy, butoxy, isobutoxy, and tert. butoxy. Linear quinacridones have been Widely described in publications and patents, and in referring to these compounds the term linear is usually omitted. Therefore, the term quinacridones (QA), as used throughout the ensuing specification, refers t'o compounds possessing the linear quinacridone structure'. Methods for. producing linear quinacridones are disclosed in U.S. Patents 2,821,529 and 2,821,539. i

Another group of compounds which may be components of the solid solutions of this invention include the quinacridonequinones, which have' the following structural where the symbols X, m, and n have the same significance as set forth above in connection with linear quinacridone. Quinacridonequinone, also known as quin(2,3b)acridine- 6,7,13,14(5,l2) tettone, appears to have been rst de-4 scribed by Sharvin in J. Rus. Phys. Chem. Soc. 47, 1260` (1915); C A., vol. 9, 3056 (1915). It is commonly prepared by condensing benzoquinone with anthranilic acid in the presence of an excess of benzoquinone to give qunone dianthranilic acid which is, in turn, cyclized Vby heating in concentrated sulfuric acid to give .quin-` acridonequinone. Substitut'ed quinacridonequinones can be prepared by using the appropriately substituted anthra- For example, 2-amino-5-chloro benzoic acid Y nilic acid. v can be used to produce a chlorinated derivative of quinacridonequinone.

A third group of related compounds which can be' A used as components of the solid solutions of this invention are the isoquinacridones having the'following structural formula:

where X is F, Cl, Br, lower alkylflower alkoxy, or combinations of these groups, andv m andfn are `integers of from 0-2, both limits being'included. .Examples of the lower alkyl substituents in the 'above formula -are methyl, ethyl, isopropyl, andY n-butyl. Examples of the;V lower alkoxy substituents are methoxy,etl1oxy,;propoxy,V

isobutoxy, and tert. butoxy. Isoquinacridone, also known as quin(3,2b)acridine-l2,14-(5,7H) dione, isdescribed by Y Eckert and Seidel, l. prakt; Chem. 102, 338-40 (l92l), who reacted a 4,6-dibromoisophthalic acid derivativew'ith A aniline to obtain 4,6-dianilinoisophthalic acid which was reaction.

The compositions of the present invention comprise where X is F, Cl, Br, lower alkyl, lower alkoxy, or combinations of these groups, and m and n are integers of from -2, both limits being included. Preferred components for the solid solutions are the unsubstituted compounds of the above formulae and their symmetrically disubstituted derivatives wherein the substituents are of the same atom or group.

The solid solutions of this invention can be prepared by contacting a physical mixture of the quinacridone components with an organic solvent, such as a dimethylformamide. Details of this method will appear hereinafter. The proportions of the components used are not at all critical when it is not undesirable to have a portion of one or more of the components in admixture with the solid solution end product. However, pure products, i.e.,

acridones and tet'rasubstituted quinacridones, Where the substituents in such compounds are of the same atom or radical.

In more specific embodiments of this invention, the following represent some of the preferred solid solutions of this invention:

(l) Solid solutions comprising quinacridone and 4,11-dichloroquinacridone, particularly the substantially pure (2) Solid solutions comprising quinacridone and 2,9-dithose which are substantially 100% solid solution, form as a result of adjusting the proportions so that all of the components can enter the same crystal lattice. These latter materials are the preferred compositions of this invention.

Some of the outstanding series of solid solutionsv which are part of this invention are set forth below:

(1) Solid solutions containing components from the group consisting of unsubstituted quinacridone and 4,11-disubstituted quinacridones wherein both substituents are of the same atom or radical selected from the group consisting of F, Cl, Br, CH3, and OCH3.

(2) Solid solutions containing components from the group consisting of unsubstituted quinacridone and 2,9-disubstituted quinacridones wherein both substituents are of the same' atom or radical selected from the group consisting of F, Cl, Br, CH3, and OCH3. V

(3) Solid solutions containing as components quinacridonequinone and/or symmetrically disubstituted quinacridonequinones wherein both substituents are of the same atom or radical selected from the group consisting of F, Cl, Br, CH3, and OCH3, usually in combination with linear quinacridones. Y i

(4) Solid solutions containing as components isoquinacridone and/or symmetrically disubstituted isoquin-Y acridones wherein both substituents are of the same atom or radical selected from the group consisting of F, Cl, r, CH3, 'and OCH3, usually in combination Awithlinear quinacridones or with quinacridonequinones.

Other components which are especially suitable for entering into the solid solutions of this invention, such asfthose described inthe above list, are 3,'10-dis\1l' stitutedk quinchloroquinacridone, particularly the substantially pure solid solutions which are brilliant magenta pigments possessing excellent lightfasteness. Such pure solid solutions contain 58-68% quinacridone, the balance (4Z-52%) being 2,9-dichloroquinacridone. A specific composition which is most preferred is a substantially pure solid solution containing 60% quinacridone and 40% 2,9-dichloroquinacridone The X-ray diffraction pattern of these substantially pure solid solutions is given in Table 7.

(3) Solid solutions comprising quinacridone and 2,9-dimethylquinacridone, particularly the substantially pure solid solutions which are brilliant magenta pigments possessing excellent lightfastness. Such pure solid solutions contain 52-62% quinacridone, the balance (3S-48%) being 2,Q-dimethylquinacridone. A specific Y composition which is most preferred is a substantially pure solid solution containing 60% quinacridone and 40% 2,9-dimethylquinacridone. The X-ray diffraction pattern of these substantially pure solid solutions is the same as that shown in Table 3. A typical pigment of this type is shown in Example 11B.

(4) Solid solutions comprising 2,9-dimethylquinacridone and 2,9-diluoroquinacridone, particularly the substantially pure solidsolutions which are Very bluish red pigments possessing excellent lightfastness. Such pure solid solutions contain 64-80% 2,9-dimethylquinacridone, Ithe balance (Z0-36%) being 2,9-difluoroquinacridone. A specific composition which is most preferred is a substantially pure solid solution containing 65% 2,9-dimethylquinacridone and 35% 2,9-diuoroquinacridone. The X-ray diffraction pattern of these substantially pure solid solutions'is given in Table 6. A typical pigment of this type is shown in Example 10E.

(5) Solid solutions comprising 2,9-dichloroquinacridone and 2,9-diuoroquinacridone, particularly the substantially pure solid solutions which'are very bluishv red pigments possessing excellent lightfastness. Such pure solid solutions contain 46-75% 2,9-dichloroquinacri- V done, the balanceA (2 5-54%) being 2-9-difluoroquin- Vacrid-one. A speciiic composition which is most preferred is a substantially pure solid solution containing 50% 2,9-dichloroquinacridone and 50%-2,9difluoro- The X-ray diffraction pattern of these A typical pigment of this type is shown in Example 9F.

V(6) Solid solutions comprising quinacridone and quinacridonequinone, particularly the substantially pure solid solutions which are lightfast pigments of a yellowish red tint., Such pure solid solutions contain 55-65% quinacridone, the balance (3S-44%) being quinacridonequinone. A specific composition which is most preferred is a substantially pure solid solution containing 60% quinacridone and 40% quinacridonequinone. The X-ray diffraction pattern of these substantially pure soli'd solutions'I is given'in Example 14. Typical pigments of this type are shown in Example 15.

The preparation of physical mixtures of colored pigments to obtain propertiesintermediate between those of the components of the mixture is a very old art. In general, the properties of such physical mixtures Vare predictable from the known properties of the components. Thus, for instance, one may prepare a simple physical mixture containing about 60% gamma phase quinacridone (a bluish red pigment)V and 40% alpha phase 4,11-dichloroquinacridone (a yellowish red pigment) to obtain a red pigment which is less blue than the unsubstituted quinacridone but still a bluish-red pigment. The lightfastness is intermediate between that of the very lightfast gamma quinacridone and the markedly inferior lightfastness of the alpha 4,11-dichloroquinacridone. In .the

X-ray diiraction pattern of the mixture, Substantiallyl all of the individual lines of the two components can be identitied.

0n the other hand, if this mixture is suspended in suicient dimethylformamide to give a fluid suspension and the suspension is heated to the boil and maintained under reiiux for an hour `or more, the product which may be isolated therefrom is a brilliant scarlet or yellowishred pigment which exhibits an X-ray ditfraction pattern which is characteristically different from the patterns of the physical mixture or either of its components. Moreover, this new scarlet pigment exhibits a degree of ,lightfastness Asubstantially equal .to that of the pure unsubstituted quinacridone, thus showing none of the degradation in lightfastness characteristic of the simple physical mixture. In all three of the properties mentioned, color, X-

lray diffraction pattern, and lightfastness, the new product exhibits characteristics which could not be predicted from the known characteristics of its components.

The disappearance of the X-ray diffraction patterns of the components and the appearance of a characteristically new pattern is indicative of the fact that the two components have crystallized together to form a solid solution with a new crystal structure. It is now found that this ability of quinacridone analogs to crystallize together to form solid solutions is characteristic of many mixtures 0f such analogs. guished from physical mixtures by the characteristic X-ray patterns which may comprise an entirely new pattern as described above, or may comprise essentially the pattern of one pure component, the patterns of the other component (or components) having disappeared. In many cases, the colors of such solid solutions are quite unpredictable from the known colors of the components. In all cases examinedsolid solutions, when formed, exhibit some properties not directly predictable from the proper- .ties ofthe components.

If a third component, 4,11difluoroquinacridone, is introduced into solid solution with quinacridone and 4,11- dichloroquinacridone by relluxing a mixture of about 55% quinacridone, 20% dichloroquinacridone, and 25% diuoroquinacridone, the resulting product has the same X-ray diffraction pattern and essentially the same tinctorial properties as the two-component system. This X-ray pattern is found to be essentially that of the 4,11-

diuoroquinacridone, and it is found to exist over a broad rangeof combinations and evenafter the introduction of a suitable amount of 4,1l-dimethylquinacridone as a fourth component.

Vdisubstituted derivatives as well as the tetrasubstituted Such solid solutions may be distin 6 derivatives. There are numerous illustrations of such combinations in the examples which follow.

FIGS. 1,-6 are diagrams which compare the X-.ray diffraction pattern of solid solutions of this invention with the X-ray diffraction pattern of physical mixtures of the individual components making up the solid solutions.

FIG. 7 is a diagram of the X-ray diffraction pattern of solid solutions formed in Examples 9-11.

FIGS. 8-10 are composition diagrams for solid solutions of this invention.

The X-ray diffraction patterns, on which much reliance is placed for evidence of solid solution, are obtained by the well known powder technique in which a Geiger counter is used to record the intensity of the dilTracted beam which is translated automatically into a curveV on which the horizontal axis records the angleof ditlraction (20) and the vertical axis, the corresponding intensity of the beam. All patterns were obtained using the Cu Ka radiation and have been recorded both as 20 (which may change with type of radiation) and as interplanar spacings in Angstrom units (A.) (which are independent of the type of radiation). Two types o f diagrams are used to show the X-ray patterns. FIG. l is an idealized curve with background scatter eliminated and the relative intensities adjusted to a maximum of FIGS. 2-6 are bar graphs which are still further idealized but much easier to use in direct comparisons. BothV types of patterns are recognized in the literature. For purposes of definition of products, the interplanar spacings will be used. In general, the values which have been recorded to three significant figures, are accurate to within about 2% and are usually reproducible on a given sample to a variation of less than 1%. Cognizance should be taken of this variance when interpreting the specication and claims. Y

For a clearer understanding of the invention, the following speciiic examples are given. These examplesare intended to be merely illustrative of the invention and not in limitation thereof. Unless otherwise specied, al1 parts are by weight.

EXAMPLE 1 60 parts of quinacridone and 40 parts of 4,11-dichloroquinacridone are suspended in about 3000 parts of dimethylformamide in a reactor equipped with avstirrer and fitted for external heating and also tted with a suitable reflux condenser. The liuid slurry, well stirred at all times, is heated to the boiling point and maintained under mild reflux for about 3 to 4 hours. Stirring is continued while cooling and the pigment is finally isolated by ltering; the excess solvent is washed out of the filter cake with water, and the paste dried to give a quantitative yield of a brilliant scarlet pigment which is highly resistant to fading under theinlluence of light when dispersedk in the usual coating composition vehicles. gives an X-ray diffraction pattern which is characterized by four strong lines with interplanar spacings of 13.8 A., 6.91 A., 6.70 A., and 3.34 A., along with ve lines of lesser intensity withinterplanar spacings of A., 4.27 A., 3.68 A., and 3.48 A.

To demonstrate the unique character of the solid solution shown above, physical mixtures of various phases of quinacridone (QA) and 4,11-dichloroquinacridone (4,11- dichloro QA) `have been prepared, in the 60/40 ratio and the properties compared with the product of Example'l.-

Thus, there is shown a physical mixture of 60% gamma phase quinacridonerand 40% alpha phase 4,'11-dichloro- 60% beta phase quinacridone and 40% beta phase 4,11- Y Table 2 summarizes Vthe X-ray diffraction lines ofthe latter mixture,'and, again, it is clear dichloroquinacridone.

that the components retained their identities.

This product also When either of the above-described physical mixtures i is treated with dimethylformamide as described above, the resulting product is the same as that shown in Example 1. Hence, in this Example 1, the starting phases of the components were not specified since they are immaterial to the final result of a product having a characteristic X-ray pattern Which is clearly different from that of either mixture. Its X-ray pattern is summarized in Table 3.

FIGURE l is a drawing of three X-ray patterns in which the dotted line represents the pattern of the physical mixture of 60% fy-phase QA, 40% ia-phase 4,1l-dichloro QA; the dashed line, the pattern of the physical mixture of 60% -phase QA, 40% -phase 4,11-dichloro QA; and the solid line, the pattern of theV solid solution of of Example 1.

FIGURE 2 is a schematic diagram of the same X-ray patterns in the form of bar graphs instead of curves.

Table 1 PHYSICAL MIXTURE 60% 'y-PHASE QA, 40% a-PHASE 4,11- DICHLORO QA Diiraction Angle 20 Lnterplanar Relative (degrees) Spacing (ang- Intensity Identification Stroms) 6.6 13. 4 Gamma QA. 12. 7. l 4,1-ichloro 13. 6. 75 Gamma QA 13. 6.55 D0. 13. 6.36 Do. 17. 5.21 Do. 19. 4.67 Intermediate Dichlor QA. 20. 4.33 Weak Gamma QA. 23. 3.72 Intermediate-- Do. 25. 3.52 Strong Dilloro 26. 3.37 do Gamr'na QA. 28. 3.18 Intermediate-- Dicliloro Table 2 PHYSICAL MIXTURE 60% -PHASE QA, 40% -PHASE 4,11-

DICHLORO QA `Diiraetion Angle 26 Interplanar Relative (degrees) Spacing (ang- Intensity Identification Stroms) 14.7 Strong Beta QA. 7.75 Weak Dilloro 7. 42 Beta QA. Y 6.80 Dichloro QA. 14. 6.23 Do. 14. 5. 98V Do. 16. 5. 50 Y Beta QA.Y 17. 5. 09 DichloroA 17.9 4. 95 D'o. 22.0 4. 04 Beta QA. 22.9 3. 88 Dichloro 3.74 do 3.62 do 3.44 Strong Do. 3. 34 Intermediate.- Do. 3. 28 Strong Beta QA.

Table 3 Y SOLID SOLUTION 60% QA, 40% 4,11-DICHLORO QA Interplanar Diffraction Angle 26 (degrees) Spacing. Intensity (angstroms) 13.8.l Strong.

6.91V Do. 6.70 Do. 5, 60 Weak. 4. 64 Do. Y 4.27 Do.

3. 68 Intermediate. 3.48 Do. 3.34 Strong.

. 8 The relative amountsV of the ingredients used in Example 1 may be varied withthe following results:

(a) y55 parts quinacridone parts 4,lil-dichloroquinacridone yields a product Whichrexhibits a principal X-ray pattern ask shown in Example 1, together with a weak pattern of 4,11dichloroquinacridone. The product is recognized as a mixture of the solid solution with excess 4,1l-dichloroquinacridone. It exhibits a somewhat yellower shade than the pure solid solution and is slightly inferior in light-fastness.

(b) 70 parts quinacridone 30 parts 4,1ldichloroquinacridone VThe excess of pure quinacridone in the solid solution shows up inthe X-ray pattern of this product as well as in the bluer shade. The product has excellent lightfastness.

EXAMPLE 2 In an alternative method of preparing the solid solution shown inV Example 1, the componentsrare pretreated by dissolving them in concentrated sulfuric acid whereafter they are coprecipitated by the rapid addition of Water. VThis pretreatmentpermits the use of a wider range of proportions in forrning the solid solutions.

60 parts ofV quinacridone and 40 parts of 4,11-dichloroquinacridone are added to 1800 parts of concentrated H2804 and stirred at room temperature until solution is complete. The solution is poured rapidly into about 10,000 parts of cold-water under good agitation. The precipitate is filtered, washed acid free, and dried, after which it is suspended in 3000 parts of dimethylformamide in a vessel equipped with a reilux condenser, and heated at the boiling point for four hours. It is then filtered from the solvent, washed free of solvent with water, and dried. The resulting product resembles that of Example l in all respects.

VIf the procedure of this example is followed, all prodv.1.1cts within the range of about 52% quinacridone to about 75% quinacrid'one (the balance being 4,11-dichloroquinacridone) are solid solutions and have the typical X-ray pattern and brilliant scarlet hue of the principal product 'FrGURE s.

of Example l.

EXAMPLE 3 The following binary combinations (parts by Weight),

when prepared in the manner set forth in Example 2 (acid pasting followed by reiiuX in dimethylformamide) Vyield products showing essentially the same X-ray patterns and very similar colorcharacteristics to the products of Examples 1 and 2:

4,11- 4,11- 4,11- Quinac- Dichloro- Dtluoro- Dimethylridone quinacquinacquinacv ridone ridone ridone 3A Y 35 65 3B-; 66 34 3C 80 20 V EXAMPLE 4.

The following mixtures of more than two components (parts Yby weight) are dissolved in sulfuric acid, drowned in water, isolated and dried, and then treated in boiling dimethylformamide as shown in detail in Example 2:

4,11- 4,11- 4,11- Qunac- Dichloro- Ditluoro- Dimethylridone quinacqninacquina@- ridone ridone ridono The nal product in each case is a solid solution exhibiting substantially the same X-ray pattern as the product of Example 1. X-ray patterns of physical mixtures and the solid solutions for 4E and 4J are shown in FIG- URE 4.

EXAMPLE 5 The following binary mixtures (parts by Weight) are dissolved in sulfuric acid, drowned in water, isolated and dried, and then treated in boiling dimethylformamde as in Example 2.

4,11- 4,11- 4,-11- Qunac- Diehloro- Ditluoro- Dimethylridone quinacquinacquinacridone ridone ridone 5A 15 85 5B 50 50 5C 15 85 The resulting/products are solid solutions which exhibit the following X-ray diffraction pattern:

Table 4 Interplanar Spacing (angstroms) Diffraction Angle (degrees) Intensity This pattern for the solid solution is typical of 4,11-y dimethylquinacridone with no evidence of the additional ingredients, whereas comparable physical mixtures show Y X-ray patterns in which the individual components can be identiied. The products are brilliant red pigments.

' The X-ray patterns of 5B and 5C, both as physical mixtures and as solid solutions, Vare-shown in FIGURE 5.

EXAMPLE 6 The following mixtures (parts by weight) containing three components, when treated by the process of Example 2, give solid solutions exhibitingrthe X-ray pattern shown in Example 5 v These products are all bright red pigments. The X-ray patterns differ from those of the corresponding physical mixturesv in which the characteristic lines of the several components can be identified. The X-ray patterns of the physical mixtures corresponding to 6A, 6D, and 613,10- gether with the solid solution pattern which is substantially identical in each case are shown in FIGURE 6L These `solid solutions are similar in X-ray pattern to those of Example 5.

EXAMPLE 7 This example illustrates an alternative method of pretreating the components prior to contact with the solvent which converts the components into a solid solution. This pretreatment involves co-milling the components in the presence of salt. Y

60 parts of quinactridone and 40 parts of 4,11-dichloroquinacridone together with 900 parts of sodium chloride are charged tov a ball mill containing'15,000 parts of Cylpebs (steel rods 1/z x 1") and of such a size that the mill is about 60% full when the complete charge is in it. The mill is rotated at about vof criticalispeed for 12-18 hours and the powder discharged from the mill through a suitable screen which willrretain the grinding elements.

This powder is added to about 1350 parts of dimethylformamide and stirred until thoroughly wet. The pasteV l EXAMPLE 8 Another series or" solid solutions was prepared by treat-V ing the following7 compositions by the method of Example 2 (acid pasting followed by reuxing in dimethylformamide):

4,11- 4,11- 4,11- Qumac- Diehloro- Dituoro- Dinlethylridone quinacquinae- Y quuacridone ridoue ridone These products are solid solutionshaving substanvtially the same XLray pattern which is essentially that of beta phase 4,11-dichloroquinacridone and v-10 parts gamma phase quinacridone hasbeen milled with salt as in Example 7, but with the inclusion of about 15 parts of di- .methylformamide inthe mill followed by isolation :Without further treatment with solvent to give a product of scarlet hue exhibiting the X-ray -diiraction'pattjern ofbeta phase 4,11-dichloroquinacridone.

EXAMPLE -9 The following mixturesofquinacridone and2,9,disub stitutedquinacridones areadded in each case to-1800 parts after which it is suspended in about 3000`parts of dimethylformamide and heated at the boiling'pointunderv Y Yreflux for four hours. VIt is then iltered from the Ysolvent,ll`4

washed free of solvent with water and dried.

Quinaeridone 2,9Dicl1loro- 2,9-Difluoro- 2,9-Dimethyl quinacridone quinacridone quinacridone Upon examination by X-ray diffraction, these products are found to have substantially identical diffraction pat terns characterized in the following Table Table 5 Interplanar Spacing (angstroms) Diffraction Angle 20 (degrees) Intensity Strong. Weak. Strong. Weak.

This pattern is isomorphous with that of the beta phase of 2,9-dichloroquinacridone. As in the previous examples, physical mixtures yield X-ray patterns in which the individual components can be readily recognized. The products of this example are intense, very bluish red pigments of excellent lightfastness.

. EXAMPLE Using the same method of treatment shown in Example 9, solid solutions were prepared from the following mixtures: v

2,9-Dichloro- 2,9-Diuoroquinacridone quinacridone 2,9-Dimethyl- Quinacridone quinacridone When the resulting products are examined by X-ray v diffraction, they all have similar patterns characterized in Y the following Table 6:

Table 6 Interplanar Spacing Diraction Angle 26 (degrees) (angstroms) Intensity l Strong. Intermediate. Strong.

Weak

Weak.` Intermediate. Weak. Intermediate.

Strong. Weak.

- This pattern is isomorphous with that of the alpha phase Y of 2,9-dimethylquinacridone. These products are intense, Vvery bluish red pigmentsof excellent lightfastness.

Intermediate.

r2 i EXAMPLE V11 Still another series of solid solutions is obtained by treating mixtures of the composition shown in the following table according to themethod of Example 9:

Quinaeridone 2,9-Diehloro- 2,9-Diuoro- 2,9-Dimethy1- quinacridone quinacridone quinacridone When these products are examined by X-ray diiraction, they all have similar patterns characterized in the following Table 7:

Y ,Y Table 7 Interplanar Spacing Diffraction Angle 2Q (degrees) (angstroms) l Intensity Strong. Intermediate. Strong. Intermediate. Weak. Y Intermediate.y Weak.

Do. Strong. Weak.

@Pimero This pattern is isomorphous with that of alpha phase 2,9-diuoroquinacridone. These products are brilliant magenta pigments possessing excellent lightfastness.

FIGURE 7 shows the X-ray'patterns of the solid solutions of Examples 9,Y 10,V and 1l, and clearly shows the differences which .characterize these products.

EXAMPLE 12 Using the Amethod of acid pasting followed by reliux in y a solvent, as shown indetail in Example 9, the following mixtures of substituted quinacridones with quinacridone are treated to form solid solutions which had unique and unpredictable properties:

EXAMPLE V1 3 y Using the method of Example 9, the following 4mixtures of substituted quinacridones readily form solid solutions with unique properties:

33 parts 4,11-diuoroquinacridone 67 parts 3',4,10,11-tetrachloroquinacridone 16 parts 4,1l-dichloroquinacridone 184 parts 4,'11-dimethoxyquinacridoneY i C. 84 parts '4,11dichloro'quinaczridoneV 16 parts 27,9-dichloroquinacridone 16 parts 4,1l-dichloroquinacridone p 84 parts 3,4,10,11-tetrachloroquinacridone 13 50 parts 4,1l-dimethylquinacridone 50 parts 4,1l-dimethoxyquinacridone parts 2,9-dimethylquinacridone 90 parts 2,9-dimethoxyquinacridone 84 parts 3,4,l0,11-tetrachloroquinacridone 16 parts 3,4,10,l1-tetramethylquinacridone 2O parts 3,10-dichloroquinacridone 80 parts 3,4,10,1l-tetrachloroquinacridone 20 parts 2,9-dichloroquinacridone 80 parts 3,4,10,11-tetrachloroquinacridone EXAMPLE 14 75 parts of quinacridonequinone (prepared by reacting 3 mols of benzoquinone with 2 mols of anthranilic in boiling alcohol, separating the yellow lcrystalline solid, and cyclizing in hot concentrated sulfuric acid) and parts of linear quinacridone, together with 900 parts vof crystalline sodium chloride, are added to a ball mill of suitable dimensions containing about 15,000 parts of Cylpebs The charge is milled in a conventional manner for about 48 hours, separated from the Cylpebs and extracted in about 4,000 parts of boiling water containing about 125 parts of concentrated H2804. After boiling the mixture for about 2 hours, it is filtered, washed free of soluble salts, and dried at about 60 C. to give a somewhat reddish-yellow pigment of good intensity and good light-fastness. Upon examination by X-rays, this pigment exhibits the following X-ray diffraction pattern:

This is substantially the diffraction pattern of pure quinacridonequinone with a slight shift toward larger diffraction angles (smaller interplanar spacings). There are no lines corresponding to the linear yquinacridone in the composition.

EXAMPLE 15 A mixture of 40 parts quinacridonequinone and 60 parts linear quinacridone is milled as described in Example 14. The powder, after separation from the Cylpebs, is added to about 10,000 parts of water containing about 500 parts of concentrated H2804, heated to the boil and boiled for about minutes, iiltered hot, washed acid free, and dried. The dry pigment is suspended in 1,000 parts of dimethyl formamide, heated at the boil under reflux for about 20 hours, cooled, filtered, Washed free of solvent, and dried to give a maroon pigment of high strength and excellent lightfastness exhibiting essentially the same X-ray diffraction pattern as that of Example 14.

When prepared by this method, mixtures within the range of about 28 to 50 parts quinaeridonequinone and 72k to 50 parts linear quinacridone exhibit substantially similar colors and a high degree of lightfastness. However, when the linear quinacridone exceeds about 65 parts, its X-ray diffraction lines begin to appear in the pattern, indicating the presence of some freequinacridone in association with the solid solution. The optimum properties appear to be found in compositions within the range of about `to 45 parts quinacridoneqninone and 65 to 55 parts quinacridone.

EXAMPLE 16 Y together with 80 parts of sodium hydroxide. 80' parts of nitrobenzene meta sodium sulfonate is added to the suspension which is then heated to 95 C., preferably in the presence of an antifoam agent, and held at this temperature with good agitation for 6-7 hours. After cooling below 60 C., it is acidiied to a pH of 4.0 with aboutY `a suitable ball mill containing 5,000 parts of Cylpebs along with 250 parts of aluminum sulfate (Al2(SO4)3.15-18H2O) 6.5 parts of tetrachloroethylene, and 2 parts of a surfaceactive agent (Emcol P-10-59-Ernulsol Corp.). After milling in a conventional manner for 12 hours, the powder is separated from the Cylpebs and extracted for 2 hours at the boil in about 1,600 parts of water containing 100 parts concentrated H2SO4. On ltening, washing free of sulfate ions and drying, there is obtained parts of a maroon pigment of high Vstrength and excellent lightfastness. Upon examination by X-ray diraction, the pattern is predominately that of Example 14 together with a line at 6.5 Y EXAMPLE 17 The following mixtures, when treated by the process X-ray diffraction patterns:

A. 40 parts linear quinacridone 60 parts 4,11-diuoroquinacridonequinone 50 parts linear quinacridone 50 parts 2,9-dichloroquinacridonequinone 50 parts quinacridonequinone 50 parts 4,1l-dimethylquinacridonequinone 50 parts 4,11-dichloroquinacridonequinone 50 parts 4,11dimethylquinacridonequinone 60 parts 2,9-dichloroquinacridone 40 parts 2,9dichloroquinacridonequinone EXAMPLE 18 Isoquinacnidone is prepared by `condensing under the iniiuence of heat 2 mols of formanilide with 1 mol of dimethyl 4,-dibromo-isophthalate in the presence of KZCOB and cupric acetate, followed by hydrolysis in anV aqueous solution of sodium hydroxide to give a solution of the disodium salt of 4,6-dianilino-isophthalic acid from'which the free acid is isolated by acidification, filtering, washing, and drying. This dianilino derivative is then .cyclized .wenn

kby heating in polyphosphoric acid, after which `the pig-` ment is precipitated by dilution with Water and then isolated in a conventional manner. Substitutedrisoquinacridon'es are made in like manner by the use of appropriately substituted aniline derivatives in this process.

50 parts of isoquinacridone and 50 parts of 4,11-dichloroquinacridone are dissolved together in 1,800v parts of concentrated H2804 at room temperature. The solution is then poured rapidly into about 10,000 parts of cold water under good agitation. The precipitate is filtered, Washed acid free and dried, after which it is suspended in 3,000 parts of dimethylformamide and heated at the boiling point for 2 4 hours. The solidis removed by filtration, washed free of solvent with water, and dried to give parts of a brilliant orange pigment of goodlightfastness. v i' n VWhen treated ina similar manner, amixture of 20 parts isoquinacridone, 50 parts linear quinacridone, and'30 parts 4,11-dichloroquiinacridone yields a solidsolution which is also a pigment of a brilliant orange color and good lightfastness. i i f These two products exhibit substantially the same X- ray diffraction pattern which is essentially that of the scarlet pigment of Example .1.

EXAMPLE 19 The following mixtures, when treated in the` same manner as shown in Example 18, give solid solutions with characteristic colors and X-ray vdiffraction patterns:

. 33 parts isoquinacridone 67 parts linear quinacridone 84 parts 2,10-dichloroisoquinacridone 16 parts linear quinacridone 84 parts 2,10-dichloroisoquinacridone 16 parts 2,9-dichloroquinacridone 16 parts isoquinacridone 84 parts 2,l0-difluoroisoquinacridone 5 0 parts isoquinacridone v 50 parts 2,10-dichloroisoquinacridone 67 parts isoquinacridone 33 parts 2,10-dimethylisoquinacridone 84 parts 2,10-dichloroisoquinacnidone 16 parts 2,lO-dimethylisoquinacridone Y EXAMPLE 20 When the following mixtures of isoquinacridone and quinacridonequinones are treated by the process of Example 18, solid solutions of characteristic properties are readily formed. v

CDFimUOPUI 50 parts isoquinacridone 50 parts quinacridonequinone 60 parts isoquinacridone 40 parts 2,9dichloroquinacridonequinone 70 parts isoquinacridone parts 4,1 l-diuoroquinacridonequinone EXAMPLE 21 Another quinacridone derivative which enters into solid solution with other quinacrido-ne compositions when mixtues are treated by the process of Example 18 is dihydroquinacridone, the intermediate in the preparation of quinacridone described in U.S. 2,821,529, as well as its substituted analogs. The following compositions are illustrative of such solidisolutions which are notable for the fluorescence introduced in sorne cases by the dihydroquinacridone.

It has heenmentioned heretofore that it is possible to vary proportions so as to produce the solid solutions inV admixture with the components making up the solutions. Such mixtures are considered to be within the scope ofy this invention, and FIGS. 8, 9, and l0 are presented to` il-V lustrate how varying the proportions of the rcomponents affects the end product produced. In all three of these figures, proportions within the shaded areas will result in y solid solutions per se; whereas, inthe unshadedareas within these diagrams, the process of lthis invention will produce the s olid solutions in admixture with greater or lesser amounts of one or more of the components, depending upon Vthe proportions selected. In certain in-V stances where products are producedufrom proportions falling in the unshaded area, it may be diiicult to Vdiierentiate 'by X-ray study a product which is'subs-tanti-ally 100% solid solution from one in which the solution is in admixture with one or more components, since the X-ray diffraction patterns of such products can closely resemble each other. However, in other instances, the proportions used to make the solid solution admixture may be such as to render the X-ray pattern of the solid solution Vadmixture clearly identifiable.

An examination of FIGJS will show' that it is a convent-ional ternary diagram in which the corners of the triangle represent the three pure components, quinacridone, 4,1l-dichloroquinacridone, and 4,1l-diuoroquinacridone, as indicated, and the three sides represent the possible binary mixtures and the area within the triangle represents mixtures containing all three components. There are three shaded area-s on this diagram within which products can be obtained which are substantially 100% solid solution.

FIGURE 9 combines in one diagram the four possible ternary kdiagrams of a four-component system which includes the three components of FIG. 8, and in addition, 4,1l-dimethylquinacridone. The central triangle indivcated by the heavier lines relates to the three substituted quinacridones,'fand the outer apexes of each of the three outer triangles are identical points representing quinacridone itself. Thus, the upper triangle is identical with that shown in FIG. 8. The areas shaded with lines parallel to the left side encompass the solid solutions illustrated in Examples 1 to 4, inclusive, each having a characteristic X-ray diffraction which suggests isomorphism with 4,11-difluoroquinacridone. The area shaded with horizontal lines encompasses the products of Examples 5 and 6 having the X-ray pattern of 4,11-dimethylquinacridone, while the small .area vshaded with lines parallel to the right side includes the products of Example 8.

If the outer triangles of FIGURE 9 are visualized as being folded into the paper to form a tetrahedron, it is then pos-sible to outline a space within the resulting solid in which are represented four component (quaternary) compositions. Example 4I is typical of the possible mixtures which form the solid solution falling within the interior of the tetrahedron.

FIGURE 10 is a composition diagram similar to FIG- URE 9 hut illustrating the combinations between quinacridone andthe 2,9-disubstitutedderivatives containing chlorine, iiuorine, and methylfgroups. It is seen that there lare 3 well-defined areas Where substantially pure solid solutions are produced.

The procedures used to obtain the solid solutions of this invention utilize the solvent action of certain powerful VVing point of the solvent.

organic solvents of which dimethylformarnide is illustrative. It should be understood that the solubility even in such a powerful solvent is small at best; nevertheless, it is sufficient to enable a slow recrystallization, whereupon the several components enter into the same crystal lattice'. Under ideal conditions, it is merely necessary to bring the components into simultaneous contact with the solvent atan elevated temperature, preferably at the boil- When solid solutions form under these conditions, they tend to approach an ideal equilibrium and frequently form pure solid solutions Ywithin a very limited range. Thus, in Example l, when the proportions are varied as little as ,5% on either siderof the optimum,the excess component shows up in the X- ray pattern as a physical mixture.

.On the -other hand, Vwhen a mixture of pigments is first `dissolved Vin strong sulfuric acid, as in Example 2, and

Y then drowned-into la large volume of water and isolated as a solid in small particle size, such products appear to be especially prone toform solid solutions on exposure to the solvent and the solid solutions frequently form over a much Wider range lof'composition than in the first 1n- 'stancej Finally, much the same purpose can he served by-a combination vof salt-milling and solvent treatment as shown l Exampleiwherein particle. sizev reduction A`is Y l? done by salt-milling and the milled powder treated with the solvent prior to removal of the salt therefrom. As a variation on this process, the solvent may be present during the milling.

The solvent used in the examples .is dimethylformamide, and it is preferred because of ready availability and economic vaiue. A chemically related solvent, also commercially available, is dimethylacetamide which is equally effective. O-ther effective solvents are tetramethylene :sulfone, dimethyl sulfoxide, ethylene glycol, diethylene glycol, glycerine, aniline, pyridine, quinoline, N,Ndi methylaniline, ethanol amine, ethylene diamine. Generically, these can be classified as strongly polar amides, sulfones, sulfoxides, polyhydroxy co-mpounds and amines.

In all of the examples, a large excess of solvent is shown. There is nothing critical about the amount of solvent used as long as it is sutlicient to thoroughly wet the pigment particles and provide suicient excess to give a fluid suspension which can be agitated. The one exception to this rule is in the case of salt-milling in the presence of the solvent where the solvent should be at least 10% of the weight of the pigment and must not exceed that amount which will permit the charge to retain the characteristics of a dry free-tiowing powder.

In the case where salt-milling precedes the treatment with solvent, the milling is an entirely conventional step of particle size reduction in which the mixture of pigments is ground in a ball mill in the presence of from about 4 to about l0 parts of an inert salt (preferably water soluble), such as `sodium chloride, for several hours up to as long as, say, 48 hours. After the milling step, it is preferable to add the powder, as discharged from the mill, to dimethylformamide or other solvent followed by a heating step and recovery of the pigment in any conventional manner.

In the case where solution in sulfuric acid is brought about and the pigment reprecipitated in small particle size by rapid dilution with water, it is customary to use at least 5 to l0 parts of sulfuric acid per part of pigment mixture. It usually requires about parts of acid per part of pigment mixture to obtain complete solution, and more may be used if required. The concentration of acid should be at least 90%, and it is advantageous to use the readily available so-called concentrated acid of about 96% purity. :Oleum may also be used. This operation is entirely conventional in the field of dyes and pigments and not at all critical. The unexpected feature is apparent when the mixtures of quinacridone pigments prepared in such a manner are treated with dimethylformamide or other solvent at elevated temperatures to give the new solid solutions. Another surprising feature of this modication of the process is that solid solutions may be obtained over a considerably wider range of compositions than when the solvent alone is used without the acid pasting step. Thus, when the pigments of Example 1 are put together in this manner, solid solutions showing no excess of either component may be obtained Within a range of ratios of quinacridone to 4,1l-dichloroquinacridones from about 52/48 to about 75/ 25 in contrast to the very limited range of compositions shown when the simple hot solvent treatment is used.

In the examples above, the principal emphasis has been placed on the systems comprising solid solutions within the series of quinacridone and its 4,1l-dichloro, diuoro, and dimethyl analogs on the one hand and the similar series of quinacridone and its 2,'9-disubstituted analogs on the other hand. However, examples are also shown of the use of the dibromo and dimethoxy derivatives in these same seriesas Well as a number of members in 3,10-disubstituted series, certain tetrachloro and tetramethyl derivatives, as well as solid solutions in which members of diiferent series have participated.

Additional examples include solid solutions in the series comprising quinacridonequinone and its substituted analogs in combination with quinacridone and substituted quinacridones as Well as combinations of various quinac- Iidonequinones. Another series of solid solutions contains isoquinacridone and its substituted analogs in various combinations of quinacridone derivatives. Finally, one example shows solid solutions containing the relatively colorless but uorescent dihydroquinacridone. Thus, the phenomenon of solid solutions .containing various combinations of quinacridone,compositions is shown to be very general.

Specific illustrations have shown the use of tluorine, chlorine, bromine, methyl and methoxy groups .as Substituents on the various quinacridone nuclei. These comprise the most readily obtainable derivatives in view yof the availability of substituted anilines. However, other lower alkyl and lower alkoxy groups such as the ethyl and ethoxy groups are contemplated as useful substituent groups. Moreover, although the convenient synthesesresult generally in symmetrical compounds, it is contemplated that unsymmetrical derivatives such as `4chlor0 quinacridone, for instance, may enter, into the solid solu-v tions.

The solid solution products of this invention olfer certain outstanding advantages in the field of colored pigments. These solid solutions Widen the range of hues available in lightfast quinacridone pigments, both towards the orange or yellow side of the spectrum and towards the blue side. Moreover, it is possible to produce solid solution pigments having outstanding lightfastness from materials which by themselves have insuiicient light stability to meet the demands of the present-day pigments market. A

Since itis obvious that many changes and modifications can be made in the above-described details without dey where X is selected from the group consisting of F, Cl, Br, lower alkyl, lower alkoxy, and combinations of these groups, and m and Vn are .integers of from 0 -2 both limits being included; said composition being characterized in that the X-ray diifraction pattern thereof is different from the sum of the X-ray difraction pattern of its constituent quinacridones.

2. The composition of claim 1 in which each of the components of the solid solution has a symmetrical structure.

3. A composition of matter consisting essentially of aV solid solution of components having formulae ofthe structure v Y H Y (i i I /N' /b X... i f X.. Y

' C/ \N/ II H Y Y where X is selected Vfrom the group consisting of F, Cl, Br, lower alkyl, lower alkoxy, and combinations of these groups, and m and n are integers of from 071, both limits of the same radical selected from the group consisting of F, Cl, Br, lower alkyl, lower alkoxy and combinations of these groups; said composition being vcharacterized in that the X-ray diffraction pattern thereof is different from the sum of `the X-ray diffraction patterns of its constituent quinacridones. Y

5. A composition-of matter consisting essentially of a solid solution of an unsubstituted quinacridone and a 2,9.-disubstituted quinacridone lwherein both substituents are of the same radical selected from the group consisting of F, Cl, Br, lower alkyl, lower alkoxy and combinations of these groups; said composition being characterized in that the X-ray ydiffraction pattern thereof is different from the sum of the X-ray ditlfraction patterns of itsconstituent quinacridones. -Y

6. A composition of matter consisting essentially of a solid solution of quinacridoneV and 4,11-dichloroquindone; said ycomposition being characterized in that the X- ray diffraction pattern thereof is different from the sum of the X-ray diiraction patterns of its constituent quinacridones.

10. A composition of matter consisting essentially of a solid solution of quinacridone and '2,v9-dimethylquinacridone; said composition being characterized in that the X-ray d-iiraction pattern thereof is different from the sum 3f the X-ray diffraction patterns of its constituent quinacridones. Y

11. A composition of matter consisting essentially of i solid solution of 2,9-dimethylquinacridone and 2,9-di- Fluoroquinacridone; said composition being characterized n that the X-ray diffraction pattern thereof is different from the sum of the X-ray diffraction patterns of its conitituent quinacridones.

1 solid solution of 2,9-dichloroquinacridone and 2,9-difluoroquinacridone; said composition being characterized -in that the X-,ray diiractionpattern thereof is different from `the sum of the X-ray kdiffraction patterns of its constituent quinacridones.

' 13. A composition of matter consisting essentially of a solid solution of quinacridone and quinacridonequinone; said composition being characterized in that theV X-ray diiraction pattern thereof is diiierent from the sum of the X-ray diffractionpatterns of its constituent quinacridones. 14. A composition of matter consisting essentially of a soiid solution of quinacridone and quinacridonequinone in which tthe proportion ofV quinacridone by l weight is -65%, fthe `balance being essentially quinacridonequinone. v

.15. A composition of matter consisting essentially of p a solid solution of by Weight quinacridone and 40% by weight quinacridonequinone.

' 16. A pigment composition consisting essentially of at least 2 diierent linear quinacridones of the formula o i ii (li Xkj: Y... X'. Y'. V

C/ \N/ t H said composition being characterized in that the X-ray' diffraction patern thereofV is different from the sum of the X-ray diffraction patterns of its constituent quinacridones.

17. A composition of matterv consisting essentially of a solid solution having'as-components a qninacridone of the formula:

and a quinacridonequinone of .the formula:

V E (inl o Y /N o b\ X. U X. \C G/ N/ Y n Y uL 1| H Y v where X is selected from the group'consisting of F, Cl, Br, lower alkyl, lower alkoxy, and combinations of these groups, and m and n are integers of from 0 2, both limits being included; said composition being characterized in that the X-ray diffraction pattern thereof is different from the sum of the X-ray diiraction patterns of its constituent quinacridones. Y

18, The composition of claim 17 in'which each of the components of the solid solution has a symmetrical structure.

, References Cited in the le of this patent UNITED STATES PATENTS Struve Jan. 28, 1958 2,821,530 Struve a Jan. 28, 1958 2,844,484 Reidinger et al. Jury 22, 195s 2,844,485 Struve 2 Iuly 22, 1958 2,844,581 Manger et al. 1 July 22, 1,958 

1. A COMPOSITION OF MATTER CONSISTING ESSENTIALLY OF A SOLID SOLUTION OF COMPNENETS HAVING FORMULAE SELECTED FROM THE GROUP CONSISTING OF: 